In order to reduce the sound level in a space it is frequently necessary to provide in this space or adjacent thereto a sound-absorbing medium. Thus in the simplest arrangement a room is fitted with drapes along one wall which tend to absorb and dissipate sound rather than to reflect it. It is also known to form the walls and ceilings of such high-noise areas as highway or underground subway stations in such a manner that they do not directly reflect sound back into the space surrounding the source. Thus the walls are formed with an array of coffers or the like to deaden sound to a limited degree.
Such arrangements have a relatively limited capacity to absorb sound. In addition they frequently require considerable maintenance, especially in the soft type of sound absorber using textile hangings, acoustic tile, and the like.